Automatically operated traffic control system



Aug. 9, 1938. F. VON OPEL 2,126,431

AUTOMATICALLY OPERATED TRAFFIC CONTROL SYSTEM 7 Filed April 25, 19s: sSheets-Sheet 1 R l l 20 40 6'0 80 7'00 12a 160 390220350 E60 E80 300 540Aug. 9,1938. F. VON OPEL 2,126,431

AUTOMATICALLl OPERATED TRAFFIC CONTROL SYSTEM fizz/@2225):

Frizz yoa z OpeZ Aug. 9, 1938. F. vofi OPEL 2,126,431

AUTOMATICALLY'OPERATED TRAFFIC CONTROL SYSTEM FiledApril 25, 19335Shets-Sheet 4 Afro/way Patented Aug. 9, 1938 TROL SYSTEM.

Fritz von Opel, Berlin-Charlottenliurg, Germany Application April ,25,

1933, Serial No. 667,868

In, Germany April 26, 1932 6 Claims.

It is known to determine the traflic density of a track or path, 1.e.,the number of .vehicles passing a control point in a unit of time,and,

to change over from the normal periodic cycle of signalling to anotherpredetermined fixed cycle when the trafiic density rises above or sinksseries of signals, for example, from the beginning of a go signal tothe. beginning of the next go signal. 7

This arrangement does not accommodate itself smoothly enough to thetrafiic, since even a plurality of predetermined cycles will not coverall variations in the continuously changing traffic 0 stream and, aboveall, since the change from one cycle to another, caused by measuring thetraffic density, cannot be performed, with sufficient suddenness. .Inorderto measure the density of traffic, the traffic must be controlled26 during a definite period of time, and since a regulation only can beeffected after the elapse of this period, the regulation, with rapidlyvarying traffic always takes place too late.

It is also known to set the go signal for a preso determined time (10seconds) by means of a vehicle passing the counting point and a timeswitch and to repeat this operation, eventually until a maximum time"(30 seconds) has been (reached, whereupon the go signal by means of a85 second time switch is switched over to the other street. Alsothisarrangement is practically of no use, since the maximum time isalready' reached by three vehicles and the following vehicles,therefore, will exert no influence at all The present invention relatestd a signal device which is influenced from the street. Ac- 50 cordingto the invention the signal apparatus of a street intersection, forinstance a signal lamp, is individually, continuously and cyclicallyoperated by means of a suitable switching device, whereby the cycle ofthe switching operations 5 is influenced by the number of vehiclespassing a a counting or control point on the track. Hereby the vehiclespassing the free street will cause a'delay in the change of signal, i.e., an extension of the green period, whereas the vehicles arriving andstopping in the blocked street will cause an acceleration of the changeof signal, i. e., a shortening of the red period. In accordance with theinvention it is also possible to consider the number of vehicles passingon both tracks simultaneously. and hereby to govern the traffic inconformity with the density of trafiic on both tracks. Suitable devicesof any kind, for instance clocklike devices adapted to perform theswitching operations at definiteintervals, may be used for creating theautomatic cycle of the signal changes and for influencing same. It hasbeen found to be particularly advantageous to change the signals'bymeans of a moving device operated by any suitable means, for instance,by a-switch drum driven by an electromotor, p

Devices of the above named kind may be influenced in numerous differentways in order to retard or accelerate the change-over of the signal. Inaccordance with the present invention a step-by-step switching gear maybe employed, which is actuated by the impulses originatingfrom thecounting points in the street.

The continuous regulation of the vehicle traflic, i. e. the changing 'ofthe signals, may now be performed by 'influencingthe speed of the switchdrum in opposite senses, i. e., by decreasing or increasing this speed.For this purpose'the apparatus may be equipped with ratchet mechanismswhich are driven by the counting impulses from the counting points onthe track. At this arrangement the regulating effect. influencing thecycle corresponds to the difference between the accelerating and theretarding impulses.

When the traffic is controlled continuously it is as already mentioned,possible to design the control devices in such a manner, that thenumbers of the vehicles driving through both streets are consideredsimultaneously and a control is exerted which corresponds with thetraffic conditions on both tracks. It is of no consequence whether twoormore streets intersect each other in the place in which the controldevice is arranged. The purpose of the device is to control the trafficin such a manner, that the total stopping time of all vehicles isreduced to a minimum. For this purpose the devices are completed anddesigned in such a manner that a division of the numbers of vehiclesdriving on both tracks is made, whereby the obtained quotient is used toinfluence the cycle in which the signals are changed. The alteration ofthis cycle is called forth by influencing the running time of theswitching apparatus by means of regulating devices, such as brakes,resistances (when motor drive is used) or the like, which are switchedin or out according as necessity arises.

A switch drum of this kind may be driven by means of any suitable force,but preferably an electric motor is used. According to the invention thedrum may also be driven by means of an electromagnetic ratchetmechanism, which is actuated by a self-releasing relay arrangement. Inthis case the switching cycle may be changed by arranging condensersparallel to the relay winding and switching these condensers in or out.For this purpose the relay is equipped with a fixed condenserthedischarge time of which is varied by means of resistances which arecoupled in series or parallel to the condenser. The switch drum may,according to the present invention, also be used for other purposes thanthat named above, for instance for reversing the polarity.

The drum may be used for switching in a constant regulating element, forinstance a constant resistance, in front of the device controlling thecycle of the switching operations. This may be made simultaneously withthe switching in of the intermediate signal (for instance the yellowlight) or at another moment. The duration of the intermediate signal ismade independent of the length of the head signal. The effect of thisregulating element may also be varied by hand and the length of theintermediate signal may therefore be varied as desired.

The above mentioned division of the numbers of vehicles driving overboth tracks or the determination of the quotient may, in accordance withthe invention, be performed by means of two step-by-step switchesadapted to switch in or out the regulating elements which control thecycle of the signal changes. The step-by-step switches are preferablynot permanently coordinated to the same street, but are exchanged(preferably by means of the switch drum) so that one switching gearpermanently operates on the street which is blocked, whereas the otheroperates on the street which is free. Each time a vehicle passes by, theappertaining switch is advanced one step, whereby the switch which iscoordinated to the blocked street at each step will switch of!additional regulating elements and the signal changing operation is madefaster. The switch coordinated to the free street will, however, at eachstep switch on additional regulating elements, whereby a slowing of thesignal changing operation is caused.

If at each step of the step-by-step switches only regulating elements ofequal magnitude were switched in or out, again only a subtraction wouldresult. In accordance with the present invention, however, theregulating elements coordinated to the series of steps of thestep-by-step switching of the step-by-step switches the number ofvehicles allowed to proceed (i. e. the numbe; of vehicles which arepresent between the counting point and the intersection) would beassumed to be equal to the number of vehicles stopped in the blockedstreet. This however, does not correspond with the real situation, sincethe traflic in the freed street has not been valued sufficiently. Inaccordance with the present invention the relation between the values ofthe regulating elements coordinated to the corresponding steps of thestep-by-step switches is made equal to the relation between the numberof vehicles which are simultaneously driving over the measuring distanceof the freedstreet and the arithmetical mean value of the number ofvehicles which are present within the measuring distance of the blockedstreet at the beginning and at the termination of the blocking. (It ishereby assumed, that the traffic is of equal intensity on both drivingtracks and is uniformly distributed over same.) It may for instance beassumed, that 60 vehicles arrive from both sides per minute at a speedof 10 m. per second, that the length of the measuring distance is 100 m.and that the normal duration of the go or stop signal (when adjusted foruniform load on both streets) is 25 seconds. In this case 10 vehicleswill permanently be present within the measuring space of the freedstreet, whereas the blocked street will show 10 vehicles at thebeginning of the blocking and 35 vehicles at the end of the blocking, i.e., an average number of 22 vehicles. The value of the regulatingelement coordinated to one step of the step-by-step switch of the freedstreet must therefore be 2 times as high as the value of thecorresponding regulating element of the switch of the blocked street.When this calculation is based on a higher speed than 10 m. per second a'still higher proportional value is obtained. If it is desired to adjustthe system for any desired sensitivity, 1. e. to attain the maximumswitching times by more or less great quotients, this may according tothe invention beperformed by alternating the relation between the valueof the regulating element of one step and the total value of allregulating elements. In accordance with the invention, therefore, eachswitch comprises several differently dimensioned series of regulatingelements, which may be selectively switched on by hand.

Besides the regulating elements switched in or out by the step-by-stepswitches, the invention also comprises a regulating element (a constantresistance, condensers or the like) which may be selectively adjusted byhand and which controls the maximum admissible duration of the go andstop signals. The present invention aims at controlling the trafliccontinuously and vehicles which already have passed the intersection onthe freed street must therefore be prevented from influencing the systemany more, i. e. vehicles which have passed the counting point andadvanced the switch one step must be subtracted when passing theintersection. This may for instance be attained by arranging a secondsubtracting device in the intersection. The same effect may inaccordance with the invention be obtained in a much simpler manner byemploying automatic means which make it possible to maintain the vehiclein the counting only for the average time which is required for passingfrom the counting point to the intersection. The distance between thecounting point and the intersection must of course be dimensioned insuch a manner,

2,126,431. that all vehicles arriving when the street is blocked canpass the counting places and stop between the counting place and theintersection. According to the invention, the step-by-step switch may bereversed in the manner that the impulse for the reversing operation isprepared by the vehicle passing the counting point. Hereby therelease, 1. e. the transmission of the impulse to the switch isinfluenced by a delaying device and does not take'place until a periodof the same length as the average driving time between the countingpoint and the intersection has elapsed.

The delaying or retarding device may comprise two mutually insulatedcontact arms adapted to slide over a number of condenser contacts. armsare so arranged, that the first arm charges the condenser with which itcontacts with the impulse caused by the primary counting, whereas thesecond arm, which reaches the same contact after the elapse of the saidperiod, transmits this charge to a relay which causes the reversing ofthe time depending on the number of vehicles which the green signalappears, the condenser holding this charge connects a constantregulating ele ment over a relay. This element may, if desired, bemanually adjustable and the connection lasts during the entire dischargetime of the condenser, so that the regulating under the influence of thequotient will not take place before this discharge has been finished.The condenser may be charged by equipping the switch for the blockedstreet with a second arm which switches on a voltage corresponding tothe position of the switching gear and the number of vehicles.

The principles on which the invention is based and the objects of theinvention have been described and a particularly simple constructionalform of the invention will be described in the following. The switchdrum may be driven. by the motor operating the lamp, but also othermeans may be used for this purpose.

The measuring places may be equipped with counting devices of anysuitable kind, for instance, electrical or optical counters, butpreferably the counting device de-cribed below should be used.

It is of course understood that in referring to a free signal it isobvious that it can be referred to as a green or g'b signal. Likewisethe inter-. mediate signal means a yellow or caution signal anda'blocked signal means a red or stop signal. Any other colorcombinations can of course be used. v

Referring to the drawings:

Fig. l is a wiring diagramshowing the electrical devices and circuitsneeded; In order to facilitate the understanding of the operation of thesystem, the s itches which are located onthe switch drum and controlledby contacts on the same are The' shown in their proper places in thediagram and a horizontal streak or dash is placed above the referencenumerals of these switches to differentiate same from the switches whichare independent of said drum.

Fig. 1a is a diagram showing the connections of the means for operatingthe speed increasing and decreasing devices, to vehicle actuatedcontrols at a street crossing.

Fig. lb is a section on the line IbIb in Fig. 1a, drawn to-a largerscale.

' Fig.1c is a diagrammatic top view of the motor together with the camsand switches.

Fig. id is a cross-sectional view of the'structure of Fig. lc taken online Id-ld of Fig. 10.

Fig. 1e is'a top view of the switches for the condensers shown in Fig.l.

Fig. 1 is a cross-sectional view, partly diagrammatic, showing a switchand 'electro-magnetic coil taken on line I fl] of Fig. 1e.

Fig. 1g is a cross-sectional view of the switch taken on line lg-lg ofFig. 1e.

Fig. in is an across the line diagram of the system.

Fig. 2 shows in the form. of a diagram the sequence of the switchingoperations performed by the switch drum and the dependency of suchoperations from the angular position of the drum. The upper half of thediagram shows the switching operations needed for one direction oftravel and the lower part shows the operations needed for the seconddirection of travel.

Referring now to the drawings, and first to Figs. la and lb, thearrangement of the system with respect to a street crossing will firstbe described. Streets N-S and W-E cross at right angles.

It is understood, of course, that the term street crossing includes anypoint where lines of trafilc intersect, such as squares, etc.

TS is a trafilc signal of any suitable type and equipped, for instance,with red lamps for stop",

green lamps for go and yellow lamps for caution.

The trafiic signal TS is operated by a switch ing drum 2 on the shaft ofa motor l. ,The drum and the motor are housed in a casing C and wires 0connect the drum 2 to the trafilc signal TS.

The street N-S is supposed to have been blocked, and its measuring placeis marked 3". The vehicles moving along the street at its righthandside, in the direction of arrow Stop, run

on a vehicle-actuated control lit at the measuring place. The controlmay be designed as shown in Fig. lb where a ramp IN is hinged at lit andforced up by a spring H6. The ramp il has a contact plate ii? on itslower face which cooperates with a. pair of contacts M3 on the baseplate of the control. Street WE is supposed to be free, and the vehiclesmoving in the direction of arrow go" run on a vehicle-actuated controlto the wires tilt! and itl of a relay it. The

relay ll controls a switch it, and the relay it controls a switch 2D.The two switches are grounded at c.-

The motor 11mm its switch drum 2, is housed in the casing C togetherwith other parts "and cirthe relay I8 is excited. The switch 20 cultswhich will be fully described with reference to Fig. l. The switch drum2, through suitable means, not shown, controls a switch 26 whichcooperates with a contact 26a in-the circuit of switch IS. The switch 26is connected to abattery, for instance, a storage battery, 25 by a wire250, and the wire includes a driving coil 23 for the speed increasingdevice, A. Similarly, a switch 21 which is also controlled from drum 2,is connected to the battery 25 by a wire 25I which includes a drivingcoil 24 for the speed decreasing device D.

The motor I is supplied with current from a system whose wires areindicated at 3 and 1, and a manually operated switch 4 is inserted inthe wire 3. Through switchingmeans to be described with reference toFig. 1, a wire 90 is connected to the system at one end while its otherend is attached to the shaft I of a step-by-step switch I0 of thedevice. A which cooperates with a set of contacts, MI. The shaft I40 01a similar stepby-step switch l4 which cooperates with a set of contactsI on the device D is connected to the system by a wire I6.

It will be understood that when a vehicle rims on the ramp I14 at B inthe blocked street N-S, the contacts I12 are closed and the relay I1 isexcited. The relay now closes the switch and prepares the circuit 250,26, zsaor the driving coil 22 for the device A so that the acceleratoris operated as soon as the switch 25 has been closed by the switchingdrum 2. Similarly, when a vehicle runs on the ramp I04 at F in the freestreet W-E, the contacts I02, I are closed and is cl sed and the circuit251, 21, 21a 0! the driving coil 24 for the device D is prepared. Thedevice D is operated as soon as the switch 21 has been closed by theswitching drum 2.

Only two vehicle-actuated controls have been shown at B and at F butobviously the crossing requires two more controls which have beenomitted as their; design and operation are exactlyv the same as for thetwo controls which have been described.

Referring now to Fig. 1, the motor circuit includes a switch havingcontact positions 5a and 5b. In the latter position, which is taken uponly during the caution or yellow period, the motor I is connected to anetwork terminal .1 over a resistance 6. Through this measure a constantyellow period is secured.

In position 5a, the motor is connected by the switch 5 and over theconduit 8 to a switch 0 which is operated by a special relay 42 as willbe described' The switch 8 connects the motor I over contact 90.directly with the arm of the step-by-step switch I0 of the speedincreasing device. Over contact 0b the connection is established througha resistance II. From the switch I0, which is shown with all resistancecut in, the circuit continues over the resistance I2 and a manuallyadjustable resistance I3 to the arm of the step-by-step switch I4 oi!the speed decreasing device D and from this point to the second terminal1 of the circuit over an additional resistance I5 or the wire I6, inaccordance with the position of the switch I4.

Referring to Figs. 1c and 1d themotor I is connected at one brush to theswitch 4 and to the switch 5 by the other brush as shown in Fig. 1. Themotor drives a worm 202 by means of its shaft 20I and the' worm 202meshes with a worm gear 203, on a shaft 204 provided with a plurality ofcam discs 205.

A plurality of binding posts 26a, 26, 26b, 44, 55a, 56, 55b, 51, 20, 29,30, 32, 5a, 5, 5b, 2), 2H and H2 are provided which are in circuit withthe various switch contacts operated bythe cams 205. The posts andcontacts 01' Fig. 1c correspond as a series to the diagram oi Fig. 2.For the switches 26, 56, and 5' two adjacent contacts 25a and 26b, 56aand 56b and 5a and 5b are provided which are adapted to be energizedselectively by their cam discs 205.

The resistances I2 and I5 are dimensioned in stages after a logarithmiclaw and are connected in such a manner to the switches I0 and 14respectively that an operation of the switch ill will cause parts orresistance I2 to be cut out and a corresponding operation of the switchI4 will cause parts of the resistance I5 to be switched in. -On accountof the logarithmic graduation of the resistances I2 and i5 thedifference between the resistances I2 and I5 which at any moment ispresent in the motor circuit will be proportional to the quotient ofnumbers of steps the switches I0 and J4 have been shifted. Theseswitches are arranged in such a manner and the number of tapping pointsis so chosen, that a correct operation is secured even when the highestpossible number of impulses within the red or green period is occurring.The switch l0 increases the motor speed and .is accordingly driven fromthe measuring place 13 of the blocked street, whereas the switch I4,which decreases the motor speed, is operated from the measuring place Fof the free street. The absolute value of the resistances I2 and I5corresponds at equal numbers of tappings, with the ratio in which thevehicle numbers in the free and in the blocked street are estimated.

The influence of the normal stop and go periods is dependent on. therelationship of the number of vehicles in the free and the stop streets.It should, to explain an example, when the traillc in the free street isto take care of 100 vehicles in a certain unit 01' time and the traflicin the stop street is to take care of 50 vehicles, then an increaseinthe number of vehicles by in the free street will exercise the sameinfluence as an increase of 5 vehicles in the stop street. As the speedof the motor I (Fig. 1) is dependent on the sum of the resistancesswitched in by the switches I0 and I4 thus the lolstvehicle must nothave the same resistance value as the 51st 'vehicle in the free street.The amount of the increase or decrease of the current from theresistances must follow in a definite relationship to the amount of theresistance cut in or cut out. This can only be attained when theresistance values between the individual'points of the switches I0 andI4 are calculated according to a logarithmic law. If for example, by the100 vehicles in the free street with the aid of the switch I0, 100 ohmsare switched in and the 101st and the 102nd vehicles switch in one ohmeach, and if the 50 vehicles of the blocked street have switched in 50ohms from the beginning of the resistance I5, then the 51st vehicle mustswitch in 2 ohms, since for the same percentage of changes of the amountof traillc a change in the sum of the resistance in the motor circuitwill not take place,

The resistance I3 may be manually adjusted to accelerate or retard themotor I in order to lengthen or shorten the minimum time intervalsbetween the green, yellow and red signals.

The switches I0 and I4 are mentioned as operated by vehicle-actuatedcontrols from the measuring places in the free and in the blockedstreets respectively. In Fig. 1, only the relay II of the controls ofthe blocked street and the relay I8 of the free street are indicated.These relays operate switches l9 and 20 in parallel with condensers 22and resistances 2I serving as sparkextinguishers when the switch isopened, the switch I9 when closed passing a current through the drivingcoil 23 of the switch III to actuate the latter and the switch 20 isclosed, similarly operating the driving coil 24 or the switch I4. Thesource of current is in this case an accumulator 25. The current flows.either over the coil 23 or over the coil 24 and over the switch I9 or 20to ground and back to battery. By means of the switches .26 and 21, theswitch'III will always becoupled to the measuring places of the blockedstreet and the switch M will always be coupled ,to the measuring placeof the free street.

The vehicle-actuated controls at B and F, the relays I1 and I8, and themeans by which the accelerator A and the decelerator D are operatedstepwise under the control of the corresponding relay and the switchingdrum 2, as described, make up counting devices.

The storage battery 25 is also connected to two circuits which-serve forreturning the switches II] and I4 to their normal positions whenthesignal is changed. The shafts of these switches also carry otherswitch arms 28 and 3| respectively, which are connected to ground overthe switches 30 and 33, respectively, when the switches Ill and I4 arenot in their starting position. When these switches are closed by theswitch drum 2, the switches I0 and I4 under the influence of. theswitches 29 and 32, respectively, (which are opened each time their ownrotary magnets are attracted) continue to rotate until the initialposition again has been reached. Here the driving circuits are opened bythe switches 28 and 3i.

The device is as before mentioned arranged in such a manner, that theduration of the free si nal always will be of such a length, that allwaiting vehicles will have opportunity to pass the intersection. For theminimum time a lower limit is set by means of the resistance I3. Inorder to secure the minimum time needed by the vehicles gathering duringthe red signal period for passing the intersection, the switch III isconnected to another switch 34 adapted to connect parts of a resistance35. The circuit of this resistance is fed from a storage battery 31 orfrom parts of the battery 25. The voltage drop over the part of theresistance 35 in circuit with the arm 3% is used to blocked street.

charge a condenser 36. The charge on this con denser is thus at a givenvoltage dependent on what part of the resistance over which thepotential is applied, that, is on the position of the arm M. In thepresent case the charge will thus be increased when the number ofresistance stages in the circuit is increased. The charge is thus alsodependent on the number of vehicles which arrive at the control place Band actuate the counting device including the relay II, and is a measurefor the number of vehicles which are present on the measuring space andwhich primarily must be considered when the signal is to be changed. Inaccordance with the invention, a switch 38 is employed, which, after thered light has disappeared, is closed during a short interval by theswitch drum 2. The charge which in this way is applied to the condenser36 corresponds, as mentioned, to the numbenof vehicles which at a givenmoment are stopping in the Shortly afterwards the switch erated,whichwill flow through the relay 42 un drum 2 closes the switch 39 andthe charge of the sistance 40 to ground.

tion of the discharge.) Simultaneously the co denser 36 is connectedtothe grid of an amplifi tube 4| over the switch 39 and a current is gethe condenser has been discharged. The rela attracts the switch 9 whichthereby is broug into the position 9b so that resistance II is cluded inthe motor circuit. The speed of motor I is therefore reduced as long asthe chargef of the condenser 36 is able to maintain the current: In thisway the number of al'- in the relay 42. ready waiting vehicles isautomatically considered.

The impulses of the relays I1 and I8andre- .sulting movements of theswitch arms Ill and I4 influence the speed of the motor I insuch amanner that the resultant speed change will correspond to the quotientbetween the'numbers of impulses. It has already been mentioned, that inthis comparison only the vehicles within the measuring space propershould be considered and that the vehicles in the free street whichalready have passed the intersection must be subtracted. The operationof the subtracting device is based on the. assumption that each vehicleneeds a definit/e average time for passing the measuring space, and thedevice comprises a relay 43 which is connected to the battery 25 andwhich relay 43 when the switch M is closed by the drum 2, re-

ceives the-current as often as the switch 20,

operated .by the free street relay I8 is operated. Relay 43 operates aswitch t5, which in closed state connects a switch arm IG to the battery3i. The arm '46, which is located on the same shaft as the arm II, is atfirst rotated by a drive magnet GI hereinafter described, at constantvelocity and hereby contacts with the contacts 46 of a number ofcondensers M, which thus are charged in turn during closed periods ofthe switch 45. The maximum number of charged condensers corresponds tothe maximum number; of vehicles present in the control or measuringspace of the free street. The switch arm ll at the same time slides overcontacts corresponding to the contacts it, but lags behind the arm M5 toan extent corresponding to" the average time which a vehicle needs fortraversing'the measuring or control space. This time will in thefollowing be named the "control time. When the arms 46 and ii arerotating their angular displacement thus corresponds to the controltime, under consideration of the angular velocity, and the intervalbetween the charging of any condenser and the discharge of same over thearm t7 and the resistance 50 is therefore equal to the control line. Thecondensers are discharged within a very short time determined by meansof a condenser M in parallel with the resistance 55. The switch arm dlis also connected to the grid of an amplifier tube 52, which, like thetube M controls the circuit of a relay t t. Each time a chargedcondenser is connected to the grid of the tube at the relay will operatea switch 5t, whichwhen switch M is in position the by means of the drum2, closes the circuit of the coil 55 of a magnet til rotating the switcharm M, which coil is connected to battery 25. When the switch ti t isoperatedand the coil .55 is energized the switch It however is reversedas compared with the efiect of the driving coil 2t. In this way thoseswitching. steps will be elimiferred to the counter for the blockedstreet.

tractlng device is formed in the manner described and the signalischanged from green to yellow, any vehicles which in this moment arewithin the control space and are prevented from passing the intersectionshould not be subtracted. The number of these vehicles must therefore betrans- This operation is performedwhen the switch drum 2 forces theswitch 56 into the position 56b and closes a switch 51. When the switch51 is closed a condenser 58 dischargesthrough the coil of aself-interrupting relay 59 thereby causing a switch 60 in the circuit ofthe drive magnet 6! to be opened and closed at short intervals. Theshaft of the switch arms 45 and 41 will then be driven by the coil 8| atahigher velocity than usual. The condensers 49 discharge swiftly and theoperations of the switch 54 are eflected at very short intervals, butinstead of the coil 55 now the driving coil of the switch I is operated.In this way the number of the vehicles which still are'in the controlspace is transferred to the I switching gear of the blocked street.

Figs. 1e, 1 and 19 show the structure of the coiland the switches 46 to48. The switcharms 45 and 41 are mounted on a common shaft and they areintermittently rotated by meansof the ratchet mechanism mounted on theshaft and operated by the coil 6|.

Fig. 2 shows in the form of a diagram the sequence of the switchingoperations performed bythe switch drum and the dependency of suchoperations from the angular position of the drum. The upper half part ofthe diagram shows the switching operations needed for one direction oftravel and the lower part shows the operations needed for the seconddirection of travel.

As will be understood the contact 38 is closed for a short timeimmediately after the switching operation from red to yellow. Hereby thecondenser 36 is charged over the switch arm 34 with the voltageimpressed over the operative part of the resistance 35, which is afunction of the number of vehicles blocked at the intersection. Theswitch 38 opens again almost at once and the switches 30 and 33 aremomentarily closed whereby the contact paths of the second or restoringarms 28, 3| of the step-by-step switches Ill, M are grounded. If thesearms are not in their initial position they will be restored under theinfluence of the self-interrupting contacts 29 and 32, which areoperated by the rotary magnets 23, 24, until the initial position isreached and the circuit is interrupted. This rotary movement ofrestoration is performed at high speed and the contacts 30 and-33 aretherefore only closed for a short time. Subsequently the switches 56 and51 are operated, as hereinbefore described. The step-by-step switchesare thus ready to operate again before the next go signal.

' When the go signal is set the switch 39 is closed and the charge ofthe condenser 36 is impressed on the grid of the tube 4|. The relay 42is energized and remains in this condition until the condenser 36 hasbeen discharged over the member 40. Hereby the resistance II isconnected to the circuit of the lamp motor as an additional resistancethus slowing down the motor and lengthening the go interval whereby allthe vehicles will have ample time to drive away.

The position of the change over switch 5 is changed at the end of eachgo signal, in order to secure a constant yellow period. The purpose ofthe switches 26, 21 and the switch 44 will be evident to anyone skilledin the art.

I claim as my invention:

1. An automatic trafllc control system for interfering lanes comprisinga signalling device including go and stop signals, for the lanes for thecontrol of the movement of trafilc thereover, an electric circuit, adrive including an electric motor in said circuit and a switching drumfor operating said signalling device to display signals forpredetermined periods dependent on the speed of said motor, a pair ofresistances in the circuit for controlling the speed of the motor eachhaving taps for cutting resistance in and out in determined steps, themagnitude of the resistance between successive taps varying according tologarithmic law, a vehicle-actuated control for the respective lanes,means responsive to actuations of one of said controls for cutting outone of said resistances step-by-step to increase the speed of the motor,and means operable substantially simultaneously with the prior saidmeans responsive to actuations of the other control for cutting in theother resistance step-by-step to decrease thespeed of said motor 2. Anautomatic traflic control system for interfering lanes comprising asignalling device including go, stop, and caution signals for the lanesfor the control of the movement of trafllc thereover, an electriccircuit, a drive including an electric motor in said circuit and aswitching drum for operating saidsignalling device to display signalsfor predetermined periods dependent on the speed of said motor, a pairof resistances in the circuit for controlling the speed of the motor, a,

vehicle actuated control for the respective lanes, means responsive toactuation of one of the controls for cutting out one of said resistancesto increase the speed of the motor, means operable substantiallysimultaneously with the prior said" means responsive to actuations ofthe other control for cutting in the other resistance to decrease thespeed of said motor, and a manually variable resistance in the circuitfor determining the period of the caution signal including meansconnected to the various resistances and controls during the respectiveperiods to connect only the last-named resistance during the cautionperiod. 3. An automatic trafiic control system for interfering lanescomprising a signalling device including go and stop signals for thelanes for the control of the movement of traific thereon, an electriccircuit, a drive including an electric motor in said circuit and aswitching drum for operating said signalling device to display signalsfor predetermined periods dependent on the speed of said motor, avehicle actuated control for the respective lanes, means responsive toactuation of one of the controls for increasing the speed of the motor,means responsive to actuation of the other control for decreasing thespeed of the motor, a condenser in said circuit, means for charging saidcondenser according to the vehicles blocked in the stop street, saidmeans including a resistance in the circuit variable in step with themotor speed increasing means and a source 01' current arranged to chargethe condenser with the voltage drop across the thus varied resistance,means for discharging said condenser when a signal changes from stop togo, and means operated by the discharge of the condenser for decreasingthe speed of the motor for the go signal.

4. An automatic traffic control system for interfering lanes comprisinga signalling device including go and stop signals for the lanes for thecontrol of the movement of tra tllc thereon. a drive for operating thesignalling device to display arcane:

eted control in the co street said control cper-.

ating the speed decreasing means, the resultant speed of the motorcorresponding to the ratio of the two members of steps through which theaforesaid two speed change means ate operated.

5. An automatic ti'elmc control system tor inter faring lanes comprisinga signalling device in= eluding stop and go signals for the lei-es tortime control of the movement cl ilfafitfi therecver, a drive memos atearialile speed operating: said signals to splay said signalsalternately to lanes for predetermined periods dependent on the speed ofthe drive, a vehicle actuated control for the respective lanes,'meansresponsive to actuations oi said control in a lane when it has the gosignal to decrease the speed of said drive, each successive actuationinr tlieidecreasing the speed and means responsive to actuations oi saidcoil-- trol in another lane, during last said go display to increase thespeed of the drive, each successive actuation further increasing thespeed, and said drive means including an electric motor and a switchingdrum for operating said signalling device to display signals forpredetermined periods dependent on the speed of said motor. 7

' 6. An automatic trafllc control system for inter- Ierlng lanescomprising a signalling device ineluding stop and go signals for thelanes for the control of the movement 01 traflic thercover, a

drive means of variable speed operating said signals to display saidsignals alternately to said lanes for predetermined periods dependent onthe speed oi the drive, a vehicle actuated control for the respectivelanes, means responsive to actuations of said control in a lane when ithas the so signal to decrease the speed of said drive, each successiveactuation further decreasing the speed, means responsive to aetuatlonsat said control enotlim" lane, doting last said go display to increasethe speed of the delve, each successive actaation farther increasingtile speed, said drive means including an electric motor and circuittherefor and a switching drum for operating saicl signalling device todisplay signals for we determined periods dependent on the speed of saidmotor, and a pair of resistances connected in said circuit to the motorfor controlling its speed to increase or decrease the speed of saidmotor.

VFRITZ v. OPEL.

